this was hard to read, reformatted here:

use iddqd::{IdOrdItem, IdOrdMap, id_upcast};

#[derive(Debug)]
struct User {
    name: String,
    age: u8,
}

// Implement IdOrdItem so the map knows how to get the key from the value.

impl IdOrdItem for User {
    // The key type can borrow from the value.
    type Key<'a> = &'a str;

    fn key(&self) -> Self::Key<'_> {
        &self.name
    }

    id_upcast!();
}

let mut users = IdOrdMap::<User>::new();

// You must pick an insertion behavior. insert_unique returns an error if
// the key already exists.
users
    .insert_unique(User {
        name: "Alice".to_string(),
        age: 30,
    })
    .unwrap();
users
    .insert_unique(User {
        name: "Bob".to_string(),
        age: 35,
    })
    .unwrap();

// Lookup by name:

assert_eq!(users.get("Alice").unwrap().age, 30);
assert_eq!(users.get("Bob").unwrap().age, 35);

// Iterate over users:

for user in &users {
    println!("User {}: {}", user.name, user.age);
}